This invention relates to a method and a device suitable for the quantitative analysis of metal elements contained in body fluids. The practice of quantitatively analyzing metal elements contained in body fluids has been increasing in importance in the field of clinical medicine, and clinical examinations. For example, zinc exists at 0.9 to 1.1 ppm in the blood serum of healthy men, but it is reported that a lack of zinc causes impairment of the gustatory sense, a decrease in reproductive functions, and growth retardation.
For example, as metal ingredients in the blood are dialyzed during dialysis, adverse reactions such as complications from zinc deficiency tend to develop rather easily. Therefore, determining the level of zinc in blood serum of patients will prove helpful in detecting zinc deficiency, and averting any complications resulting from said deficiency. It is preferable that this quantitative analysis be performed immediately after collection at a medical institute which collects body fluids. In actuality, however, most of the body fluids collected arc sent outside for analysis, because the conventional method requires skilled operations, and it takes a long time to get results.
In order to effectively determine the concentration of metal elements in body fluids, it is necessary to remove any proteins from the sample prior to analyzing it. This is necessitated by the fact that proteins generally impede the quantitative analysis of metal elements in body fluids. The protein is liberated by adding a deproteinizing agent such as an acidic solution of trichloroacetic acid, and further separated by centrifugation. Then, after performing a pre-treatment corresponding to a target metal element, the deproteinized sample is introduced into a quantitative analysis device.
As to prior art, please refer to "Conventional Method (Centrifugation and Absorptiometry) for Analysis of Metals in Body Fluids by T. Makino, M. Saito, D. Horiguchi and K. Kina: Clinical Chimica Acta, Vol. 20, 127-135 (1982)".
The following problems are associated with the conventional method, mentioned above:
(1) A large amount of sample of about 0.2 to about 0.5 ml or more is usually required for the analysis.
(2) Since a series of analytical steps from deproteinizing to quantitative measurement are performed by batch system, it takes a considerably long time to obtain the results of analysis.
(3) Since the analytical operation is performed in an open system, the probability of contamination of the body fluid sample during the operation is greatly increased.
(4) A skilled technician is needed because the analytical operation is complicated.
(5) The rate of error in the measurement of the concentration of metals is great.
On the other hand, the so-called "flow injection method" is known as a continuous analysis method. This method requires feeding a reagent solution into a tubule by a non-pulsatory quantitative pump, etc., injecting a sample solution into the reagent, mixing the reagent and the sample with one another in the tubule, and then introducing the reacted solution into a quantitative analysis device. In this method, the required amount of the sample is small; the likelihood of contaminating the sample is almost nil because the steps of mixing, reaction, and dilution are performed in the tubule; and an automatic determination of the concentration of the target metal element can be performed with high precision and within a short period of time. Further, since it is possible to control the dispersion of the sample by adjusting the fluid conditions of the system, this method is suitable for analyzing a large number of samples within a short period of time by appropriately changing the conditions according to circumstances. Additionally, the assembly and maintenance of the device is easy and inexpensive.
As to prior art, refer to "Conventional Method of Flow Injection Analysis by T. Deguchi, R. Takeshita, A. Tanaka and I. Sanemasa: Bunseki Kagaku Vol. 37, 247-252 (1988)".
However, direct quantitative analysis of metal elements contained in body fluids by the flow injection method have not been performed so far. This is because, the centrifugal step for isolating proteins from the sample was thought to be indispensable to this method. Thus this method was not deemed suitable for determining the concentration of metal elements in body fluids.